Lower Tertiary Foraminifera from South East Oman

Abstract:

Over 250 samples were collected over three field seasons from the SE Oman Mountains. Fortyone species of planktonic Foraminifera (belonging to 7 genera) and twenty-eight species of larger benthonic Foraminifera, (belonging to 13 genera) are figured (both by SEM and optical photography) from the Wadi Musawa and Wadi Suq sections. Nine planktonic foraminiferal
zones are formally recognised between the Upper Palaeocene(P 4) and upper Middle Eocene
(P14). The known stratigraphic distribution of these species was used to recognise the zones P 5, P8-P9 as equivalentt o standard zones of Blow, 1969,1979, whilst strata considered generally equivalent to P4 and PIO-PI4 in the Wadi Musawa section are zoned on the basis of the local
range. Younger sediments can only be dated on larger Foraminifera. A possible hiatus
representing the planktonic zones P 6/P7 is tentatively identified. Fifteen lithostratigraphic units are recognised and formally described from three formations: the Abat Formation( units A-D), the
Musawa Formation (units E-L) and the Tahwah Formation (units M-0).
The ages of the Abat and Musawa formations are redefined and are shown to be significantly
older than previously published. Biostratigraphical and palaeoenvironmental data from both the planktonic and the larger Foraminifera has been used in conjuction with the lithostratigraphy to
construct a sequence stratigraphy, in which several cycles have been recognised. Some of these cycles may correlate with the global sea-level cycles of Haq et al. (1987) and include TA2.3 and
TAM, Whilst others are local due to tectonically induced regressive and transgressive events.
Information not only from the Foraminifera but also from radiolaria, ostracods and molluscs has been used to reconstruct the palaeoenvironment for the Omani Palaeogene. Parts of the Lower and Middle Eocene contain in-situ larger Foraminifera indicating deposition in a shelf
(dominantly mid to outer) setting.
During the late Palaeocene, most of the early Eocene, part of the middle Eocene, and the entire
late Eocene/early Oligocene mixed assemblages of planktonics and shallow water benthonics
were the dominant Foraminifera. The occurrence of the these two assemblages in deepwater
sediments indicates a substantial period of time in which penecontemporaneous uplift and
resedimentation of carbonate shelf deposits into deeperwater occurred. A number of new larger and smaller benthonic Foraminifera are described and one planktonic foraminifer renamed.

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